Microbiological influenced corrosion (MIC) can lead to significant problems in piping networks of fire suppression systems. Water borne microbiological entities, such as bacteria, molds and fungi, brought into a piping network of a sprinkler system with untreated water, feed on nutrients within the piping system and establish colonies in the stagnant water within the system. This occurs even in so-called “dry” sprinkler systems where significant amounts of residual water may be present in the piping network after a test or activation of the system.
Over time, the biological activities of these living entities cause significant problems within the piping network. Both copper and steel pipes may suffer pitting corrosion leading to pin-hole leaks. Iron oxidizing bacteria form tubercles, which are corrosion deposits on the inside walls of the pipes that can grow to occlude the pipes. Tubercles may also break free from the pipe wall and lodge in sprinkler heads, thereby blocking the flow of water from the head either partially or entirely. Even stainless steel is not immune to the adverse effects of MIC, as certain sulfate-reducing bacteria are known to be responsible for rapid pitting and through-wall penetration of stainless steel pipes.
In addition to MIC, other forms of corrosion are also of concern. For example, the presence of water and oxygen within the piping network can lead to oxidative corrosion of ferrous materials. Such corrosion can cause leaks as well as foul the network and sprinkler heads with rust particles. The presence of water in the piping network having a high mineral content can cause scaling as the various dissolved minerals, such as calcium and zinc, react with the water and the pipes to form mineral deposits on the inside walls which can inhibit flow or break free and clog sprinkler heads, preventing proper discharge in the event of a fire.
There is clearly a need for a piping network for sprinkler systems wherein scaling, oxidative corrosion and MIC is mitigated so as to be insignificant.